I have been enjoying MeshCAM for several years now, it is great program. I have run into an issue tonight however.

This is a 2D part, I am simply cutting out shapes, holes, and pockets from a sheet of .75" MDF with my CNC router. The program wants to machine the top of the stock on this particular piece during the parallel finish phase, even though I have selected the "Don't machine Top Of Stock" checkbox.

My part was created in SolidWorks and saved as an .stl file.

Is there any idea why it is ignoring this for this particular part? I have not had this problem before. I am using MeshCAM 7 with Windows 10.

First I drew a block in SolidWorks that is 100mm x 300mm x 19.05mm thick. I put a through hole and a blind hole 10mm deep in it.

I saved it as a .STL file.

I opened it in MeshCAM 7, and generated a 3D toolpath. I selected "Don't Machine Top Of Stock". I get the tool path that I want where the top of the block is not being machined (See Test Block 1 Image)

Test Block 1

Test Block 1.jpg (242.78 KiB) Viewed 563 times

Experiment 2:

I then changed the dimensions of the block in SolidWorks to 300mm x 300mm x 19.05mm thick. I left the through hole and the blind hole unchanged.

I saved it as a .STL file.

I opened it in MeshCAM 7, and generated a 3D toolpath. I selected "Don't Machine Top Of Stock". I get the tool path that I do NOT want (Test Block 2 Image) where the top of the block IS being machined (See Test Block 2 Image)

Test Block 2

Test Block 2.jpg (417.76 KiB) Viewed 563 times

The Tool Path Parameters are the same for both, and I have attached them as well.

Toolpath Parameters

Toolpath Parameters.jpg (141.35 KiB) Viewed 563 times

Does anyone have any idea why it is ignoring the command for the larger part? Is there something I am missing?

you were right. I have the same results like you with your two experiments. Don't know why.

And figured out some more errors :

#1 I first open the smaller stl file and try to create a toolpath. Then I open the larger stl file which opens correct but an empty stock shape of the small one is visible below the solid stl above. Closing MesCAM aand restarting makes it work correct again.

#2 I noticed that MeshCam hangs sometimes and opened the taskmanager. There I see 2 or three meshcam.exe running with different sizes in memory . Killing the smaller one(s) makes the last one continue running.